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Old 07-30-2013, 06:22 PM   #1
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Hot water from cold pipes, plumbers are stumped


The problem
When faucets in our house are first used, you get a long wave of hot water from the cold water side. After a while, maybe 1-2 minutes, the water will finally get cold again. And when I say "hot" I mean too hot to touch. Things used to work fine, so this isn't a fundamental screwup in the plumbing.

The plumbing
I have a two-story home with recirculating hot water (dedicated return pipes). The water heater (WH) is in the garage, and was replaced about three years ago. It's a Kenmore 75 gallon unit, and I think our problems started sometime after the WH replacement. Originally, the hot water return went to the recirculating pump, and then into a T-connector on the WH cold input. The first fix attempt (which was well after the new WH was installed) replaced the recirc pump with a Grundfos UP10-16BU ATLC (which has in internal check valve), and replumbed the water return line to enter the WH through the lower drain spigot. This seemed to help a little with our problem, but didn't fix it.

What I've done to diagnose
For all faucets or other appliances that connect to the hot water and have accessible cut-off valves, I tried turning off the hot water to see if that helped. None made any difference. We still have about six bath and shower valves where the pumping is in the wall so I can't turn off the hot side manually. I believe all of them are Delta brand. I also tried unplugging the recirculating pump: this effectively reversed the problem: we'd no longer get hot water from the cold taps, but then we'd get cold from the hot side for a couple minutes. Basically, what you'd expect without recirculation. I've had two plumbers come check out my system. The first "checked" all of my in-wall faucets and declared them to be fine, replaced my hot water recirculating pump, and rerouted the return water line. That didn't fix the problem. The second plumber wanted to install a check valve in series with the pump, but since the pump has an internal check valve I wouldn't let him. I became suspicious that we were getting convection (thermal) mixing, so I had plumber #2 put a 8-inch vertical rise and fall in the cold water input to the WH (like an upside-down sink trap; I think this is called a heat trap). But that made no difference.

Both plumbers suggested putting in a cold water check valve to prevent backflow from the WH, but I'm reluctant to do this. For one thing, I believe CA plumbing code requires that I also install a thermal expansion tank, which is extra cost, annoyance, and potential maintenance hassle. But more importantly, everything used to work fine without a cold water check valve. There should be no way for hot water to be pumped through the cold water system, unless I have some crossover connection between my hot and cold lines.

Ideas? Can Delta mixer valves leak from hot-to-cold without water coming out of the fixture?

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Old 07-30-2013, 06:31 PM   #2
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Hot water from cold pipes, plumbers are stumped


I suspect one or more shower cartridges are the problem

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Old 07-31-2013, 07:07 AM   #3
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Hot water from cold pipes, plumbers are stumped


Where are you?

The last time we saw this problem,the member was from southern California and the pipes were run through a hot attic----and were heated up there--no plumbing problems at all---
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Old 07-31-2013, 07:30 AM   #4
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Hot water from cold pipes, plumbers are stumped


Since turning off the pump stops the issue it can be concluded that there is at least one fixture passing water. Any one handled device that mixes hot & cold could be at fault.

I would get up in the early in the morning before any water is used and feel the fixtures for warmth. The offending device(s) will be warm while the ones that are OK will be ambient.
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Old 07-31-2013, 08:25 AM   #5
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Hot water from cold pipes, plumbers are stumped


The cold water pipe going into your hot water heater ---- if you hold the pipe 3 feet from the water heater, is it hot or cold?

On page 5 of this manual http://www.pexuniverse.com/docs/pdf/...ion-Manual.pdf they specify allowed and not-allowed orientations for the pump. Is your pump mounted in an allowed orientation?
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Old 07-31-2013, 08:35 PM   #6
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Originally Posted by SPS-1 View Post
The cold water pipe going into your hot water heater ---- if you hold the pipe 3 feet from the water heater, is it hot or cold?
Unfortunately, there are only about two feet of pipe before it enters the wall, but it feels pretty consistently warm along those two feet.

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Originally Posted by SPS-1 View Post
On page 5 of this manual http://www.pexuniverse.com/docs/pdf/...ion-Manual.pdf they specify allowed and not-allowed orientations for the pump. Is your pump mounted in an allowed orientation?
Yes, it's mounted with the pipe vertical, flowing down, and the motor extending horizontally from the wall, just like cover illustration.

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Old 07-31-2013, 08:38 PM   #7
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Hot water from cold pipes, plumbers are stumped


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Where are you?

The last time we saw this problem,the member was from southern California and the pipes were run through a hot attic----and were heated up there--no plumbing problems at all---
I'm in Northern CA. I saw the thread you're referencing during my pre-posting searches, but I'm pretty confident that's not my situation. Evidence in support of my position:
  • We get the problem first thing in the morning, after the house has cooled down.
  • We get the problem year round, even on overcast or cold days.
  • The water is really, really hot, not just warm like the prior poster's.

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Old 07-31-2013, 08:42 PM   #8
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Hot water from cold pipes, plumbers are stumped


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I suspect one or more shower cartridges are the problem
That's what I suspected, too, though I contacted Delta and they insist that if their cartridges leak, this will be evident by water coming out of the fixture. Maybe that's just marketing talking, but I had previously read similar assertions (it can't happen with Delta cartridges, only with certain other brands).

Still, this seems the like the best candidate solution. The problem is that my house has five of these cartridges, and at $40 each it's pretty pricey to replace them all speculatively, and really time-consuming to replace them one-by-one (each time I have to drain the water lines, replace the cartridge, turn water back on, and wait several hours to see if the problem went away).

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Old 07-31-2013, 08:46 PM   #9
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Since turning off the pump stops the issue it can be concluded that there is at least one fixture passing water. Any one handled device that mixes hot & cold could be at fault.

I would get up in the early in the morning before any water is used and feel the fixtures for warmth. The offending device(s) will be warm while the ones that are OK will be ambient.
This is a good idea. I tried it this morning, but all of the handles felt room temperature to me.

I have an infrared thermometer hidden somewhere in my house (ahem!), and once I find it I'll try the experiment again using more precise readings. I'd really love to pinpoint one (or two) suspect fixtures.

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Old 07-31-2013, 08:47 PM   #10
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Hot water from cold pipes, plumbers are stumped


Last Summer everyone across the U.S. during the Heat wave, had issues with incoming water being warm, even though most of us live in areas, that the pipes are at least 6 feet underground, but the problem was from the water being warm, when it was coming from the plants.

Seabeast, take a thermometer such as this http://www.walmart.com/ip/Progressiv...n-Red/16630653 and post what the reading is.
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Old 07-31-2013, 08:53 PM   #11
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Hot water from cold pipes, plumbers are stumped


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Originally Posted by seabeast View Post
This is a good idea. I tried it this morning, but all of the handles felt room temperature to me.

I have an infrared thermometer hidden somewhere in my house (ahem!), and once I find it I'll try the experiment again using more precise readings. I'd really love to pinpoint one (or two) suspect fixtures.

-Seabeast
Did you run the cold water or just feel the handles?
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Old 07-31-2013, 08:56 PM   #12
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Did you run the cold water or just feel the handles?
I just felt the handles.

What was the right answer to that question?
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Old 07-31-2013, 09:04 PM   #13
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Hot water from cold pipes, plumbers are stumped


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Originally Posted by seabeast View Post
I just felt the handles.

What was the right answer to that question?
I think you gave the right answer but I don't know how accurate the test is

Have you pulled a cover plate off a shower/tub valve and checked for integral stops?
They are small stop valves located at the H&C inlets w/screwdriver slots.
If you have them- turn them clockwise to kill the water to the mixing valve
This will stop any cross over at that location.
I can't say if Delta's will or will not cross over- but its worth a look.
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Old 08-01-2013, 06:26 AM   #14
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Hot water from cold pipes, plumbers are stumped


The handles may be too insulated from the fixture by plastic cartridge parts. Check a metallic area or better yet the connection pipes on sink faucets and the cold side of the valve body on showers. (requires removal of handle and escutcheon plate)
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Old 08-01-2013, 03:39 PM   #15
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Originally Posted by gregzoll View Post
Last Summer everyone across the U.S. during the Heat wave, had issues with incoming water being warm, even though most of us live in areas, that the pipes are at least 6 feet underground, but the problem was from the water being warm, when it was coming from the plants.

Seabeast, take a thermometer such as this http://www.walmart.com/ip/Progressiv...n-Red/16630653 and post what the reading is.
Last night I checked the kitchen faucet. The cold water temp started at around 78, then after 10-15 seconds rose to 110, held that temperature for another 10 seconds or so, and then slowly dropped back to 78. Interestingly, when I then turned the handle to HOT, the maximum I measured was also 110. This was surprising, since I have my WH set to "B", which the manual claims is 140F. I don't expect 140 at the fixture, but with HW recirculating I would expect to get above 120F at least. To be fair, my wife had recently been doing dishes in the sink, so some HW had been used, but surely not enough to make a dent in my 75 gallon WH.

Later, I repeated the test at an upstairs bathroom and got similar readings for both hot and cold.

This morning I did the test again. This time the HOT side got a little above 120F (hard to read precisely on that tiny thermometer dial), but the cold side still peaked at around 110.

On the topic of WH temperature, the last plumber I consulted on this problem was alarmed that I had my WH temperature set to a little above "C". He rattled off a long list of disasters this would surely cause, including hot water from my cold taps, melted washers, blurred vision, flatulence, etc. To humor him, I dropped the temperature down to "A" for a night to see if that would solve my hot-in-the-cold water problem, which of course it didn't. But then I did some research on what A, B, and C meant, and decided to go with "B". Supposedly on my Kenmore WH, A=130F, B=140F, and C=150F. The question buried in this is "what are the odds that 'B' really corresponds to 140, and if they're not good, what's the recommended method of determining the actual WH temperature?"

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